Video: Working with the Adaptive Subdivision sampler

We come now then to the final choice that V-Ray offers in terms of image sampling engines which is of course the adaptive subdivision system. Again, we need to come up to our Render Settings window, if we want to enable that, so let's open that dialog. Come to the V-Ray tab. Inside our Image sampler rollout, we want to use our drop-down and enable the Adaptive subdivision system. In here we get access to of course our control parameters. We have the maybe familiar Min and Max rate settings, we have a Threshold setting as well.

This course introduces the features of the V-Ray 2.0 rendering engine and demonstrates how to extend the range of Maya with its state-of-the-art tools, such as irradiance mapping, fur and hair textures and shaders, and stereoscopic 3D rendering. The course covers critical concepts such as creating basic materials, image sampling, color mapping, subdivs, and lighting, as well as the Render Elements, RT, and physical rendering workflows in V-Ray. Exercise files are included with the course.

Working with the Adaptive Subdivision sampler

We come now then to the final choice that V-Ray offers in terms of imagesampling engines which is of course the adaptive subdivision system.Again, we need to come up to our Render Settings window, if we want to enablethat, so let's open that dialog.Come to the V-Ray tab.Inside our Image sampler rollout, we want to use our drop-down and enable theAdaptive subdivision system.In here we get access to of course our control parameters.We have the maybe familiar Min and Max rate settings, we have aThreshold setting as well.

But there are one or two options in here that I just worth making note off.For instance we have this Edges option that when checked, will allow us toessentially supersample the edges of geometry in the scene.We have this Normals option, which along with this Threshold value will allow usto supersample any surfaces that have widely varying normal directions.One option that we definitely will want to leave checked is this Jitter option.It basically allows the samples in the system to be slightly offset to bedisplaced a little bit so as to produce better antialiasing of horizontaland vertical lines.

Our Min and Max rate values do work again a little bit differently from thestraightforward subdivisions used by the other two image sampling engines.We do need to be careful when setting values in here.To demonstrate what I mean, if we use a Max rate value of 0 in this system, thenwe are essentially using a single sample per pixel.If we set a value of 1 in there, then we will be using four samples per pixel.But if we just jump up to a Maximum rate value of 2, we are all of a suddenusing 64 samples per pixel.

And that kind of exponential increase continues as we step up the Max rate values.If we are using a Max rate of 5 or 6 in our scene, we could potentially be usinghuge numbers of samples per pixel that would definitely slowdown the system, sojust be careful when entering values in here.As of course we have our other image sampling engines, we want to work with someparameters in here and see how they affect the rendering of our scene.Throughout this exercise we will be working with an Adaptive subdivisionMinimum rate of -2.

This means that the system can undersample wherever it feels it is appropriate.A Minimum rate setting of -2 means that the system can go as low as using asingle sample for four pixels in our rendered image as we say the Adaptivesubdivision system is able to perform this kind of undersampling very nicely.We also of course want to make change to our Max rate.We are going to set this to a value of 0, this means we are using a singlesample per pixel and we are going to make our Threshold value 0.1.

This means the system is not really that sensitive to adding extra samples into the render.Now of course we can jump into Adobe Bridge and navigate to ourpre-rendered images.So come into our assets folder, into the Ch06 folder.Let's grab our Adaptive subdivision (Adv_ SubDiv) renders and select the first one.And if we just maximize this by using the Spacebar and then the left mouseclicking, you can see perhaps not unsurprisingly that we have a very lowquality image, we have lots of breakup along the edges of our geometry, lots ofnoise in the scene.

Although the lines in our materials not faring too badly, our noisy material interms of our vast object and our surface here, definitely missing some detail,but still not looking too bad.And we have a reasonably fast render time of a minute and 18 seconds.Clearly though we need to do work here.So let's go back into Maya.Let's set our Max rate up to a value of 2 and with a no other changes, we'll goand examine how that will affect the rendering of our scene.Let's select our second image and maximize that.

And you can see we have improved things, the edges of our geometry looking muchcleaner, our lines, definitely they are working very nicely.We still have lots of noise in the scene of course and we are still at threeminutes and twelve seconds, so pretty fast we could definitely use this as atest render for sure, but if we wanted to clean this up for our final output, westill have a little bit more work to do.So let's jump back into Maya and come to our rate settings.Of course as with the Adaptive DMC system, increasing our Maximum rate value isnot always the best thing to do.

Sometimes we need to make the system a little more sensitive to using thesamples available in the Max rate.In this instance, if we add zero into our Threshold setting, so 0.01 and if wewere to go back to Bridge and pull up our third render, you would see thatjust making that quick tweak to our Threshold value has really helped clean upthe noise in our image.Still a few little areas that we may want to work on, may want to clean it, wecan see there is some small noise detail in the shadow, small noise detail onthis diffused brick and of course we are all the way up to 21 minutes now.

But we can tell that what we would need to push things a little bit further ifwe really wanted to clean up this scene.So let's come and set a Max rate setting of 3, we are going to leave ourThreshold value where it is and if we examine our final Adaptive subdivisionrender, you can see that we really do clean things up very nicely indeed.If we were being really picky, we would still say that some of our shadow areashave a little bit of noise.We do need to remember that the DMC sampler threshold will still be affectingnoisy render effects in the scene.

So we may need to tweak those a little bit even though we are working with theAdaptive subdivision system to clean those types of effects up.Of course we are all the way up to an hour and five minutes, so we have reallyincreased our render times.And really that is because the Adaptive subdivision system is not generallyspeaking good at working with scenes such as the one we've set up here, one thathas lots of noisy or blurry effects in it.The Adaptive subdivision system works well with scenes with lots of black orplane color in them, scenes that have very few noisy effects, it can give youvery fast and clean renders from such a shadow.

Of course as we have mentioned its weakness is with noisy effects in the sceneand another big one is the fact that it is extremely memory intensive.The Adaptive subdivision system holds all of its sampling information in memoryso we can find ourselves running into out of memory errors with big scenes.That having been said, if we choose the scenes to use this system on wisely, ifwe play to its strengths, then the Adaptive subdivision engine can be a powerfultool at our disposal.What we want to do next then is really have a look at how the final renders fromeach of our image sampling engines compare.

Let's see how they stack up against one another in terms of the speedand quality of output.

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